This invention relates to a plasma-addressed display device for displaying a matrix of M rows of N pixels wherein N is larger than M, the display device comprising: a layer of electro-optical material sandwiched between elongated data electrodes and plasma channels, the data electrodes and the plasma channels crossing each other for obtaining overlapping areas constituting pixelelements corresponding to the pixels, each plasma channel comprising spaced first and second electrodes, a plasma driver circuit coupled to the first and the second electrodes for selectively activating the plasma channels for selecting pixelelements associated with the activated plasma channel, the first electrodes being interconnected in a number of first groups and the second electrodes being interconnected in a number of second groups such that each of the first groups includes no more than one electrode of each of the second groups, and a data driver circuit coupled to the data electrodes for supplying data signals to the pixelelements in response to a video information.
EP-B-0,325,387 discloses a plasma-addressed liquid crystal display, commonly referred to as a "PALC" display device. The known PALC display device comprises: a first substrate on which parallel transparent column electrodes are deposited, a second substrate which has parallel sealed plasma channels corresponding to rows of the display, and an electro-optical material such as a liquid crystal material sandwiched between the substrates. Each of the plasma channels of the second substrate is filled with a low pressure ionizable gas, such as helium, and contains spaced cathode and anode electrodes along the channel for ionizing the gas to create a conductive plasma. The channels are closed off by a thin transparent dielectric sheet. Each of the plasma channels crosses all of the column electrodes to form a matrix of overlapping regions. The overlapping regions correspond to pixels of the electro-optical material.
The operation of the PALC display device is, by way of example, further elucidated in case the electro-optical material is liquid crystal material (LC-material). The plasma channel acts as a row switch capable of selectively addressing a row of liquid crystal pixel elements (LC-pixels). Successive lines of data signals representing an image to be displayed are sampled at column positions and the sampled data voltages are respectively applied to the column electrodes. All but one of the row plasma channels are in the de-ionized or non-conducting state. The plasma of the one ionized selected plasma channel is conducting and, in effect, establishes a reference potential on the adjacent side of a row of LC-pixels, causing each LC-pixel to charge to the difference of the reference potential and the column potential. Then, the ionized channel is turned off for isolating the LC-pixel charge and storing the data voltage for a frame period. When the next row of data appears on the column electrodes, only the succeeding plasma channel row is ionized to store the data voltages in the succeeding row of LC-pixels, and so on. As is well known, the attenuation of each LC-pixel to backlight or incident light is a function of the stored voltage across the pixel.
Further, two possibilities are disclosed to select the plasma channels one by one. The first possibility shows that one electrode of each plasma channel is connected to a reference potential. So, all these electrodes can be interconnected to receive the reference potential. The remaining electrode of each plasma channel is connected to receive a pulse signal. The plasma channels are selected one by one by supplying one pulse signal with a voltage pulse which has a value with respect to the reference voltage that is large enough to ionize the plasma, while all other pulse signals supply a voltage which has a value with respect to the reference voltage that is too low to ionize the plasma. Assuming a PALC display device with N rows of pixels, N pulse drivers are needed to supply the N pulse signals to the panel. Such a panel has 2N connections for supplying the pulse signals and the reference voltage to the electrodes of the plasma channels. The second possibility shows that the number of pulse drivers decreases by taking together in groups both the anode and the cathode electrodes. The groups are chosen such that each of the anode groups includes no more than one electrode of each of the cathode groups, and in the same way, each of the cathode groups includes no more than one electrode of each of the anode groups. Each anode group is electrically isolated from the other anode groups, and each cathode group is electrically isolated from the other cathode groups. The adjacent cathode-anode electrode pairs are each located in one channel, and the channels whose electrodes form any one of a first group thus include no more than one electrode of any one of the second group. Each channel thus corresponds to a respective unique combination of one cathode group and one anode group. Assuming again a PALC display device with N rows of pixels, both the cathode and anode electrodes are taken together in groups of N.sup.1/2 lines, with one pulse driver per group. This leads to 2N.sup.1/2 instead of N pulse drivers, and if the connections in each of the groups is made on the PALC display panel to 2N.sup.1/2 instead of 2N connections.
The known display device has as a drawback that still a lot of data drivers are needed to supply the data signals to the column electrodes.